Spin-valley transport properties in a silicene velocity superlattice

Using the transfer matrix method, the valley- and spin-dependent transport properties in a silicene velocity superlattice under extrinsic Rashba spin-orbit coupling, are theoretically investigated. Silicene velocity superlattice includes the silicene sheet, in which the electrostatic potential and the Fermi velocity vary in space. It was found that through adjusting the Fermi velocity, number of velocity barriers and Rashba spin-orbit interaction, the transmission probability, with and without the spin-flip can be controlled. The results show that increasing the Fermi velocity results in the reduction and enhancement of the oscillation amplitude and oscillation period of the spin-dependent conductance, respectively. Specifically, in the case of Fermi velocity ratio (the Fermi velocity inside barriers over the Fermi velocity outside barriers) being smaller than one, fully valley polarized current can be observed. However, when the Fermi velocity ratio exceeds one, increasing the Fermi velocity leads to the decrement of valley polarization. Furthermore, the spin polarization is controllable via the Fermi velocity ratio.